Fix ST3 issues and command panel

1. decode() is removed from strings in Python3, as well as the string-escape codec. I've removed unnecessary encoding and decoding so the code works for both ST2 and ST3.
2. ST3 does not allow calling show_quick_panel from on_done, so we need to work around with a timeout (http://www.sublimetext.com/forum/viewtopic.php?f=6&t=10999).